Special Weather Statement, NWS Raleigh, NC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1045 PM EDT MON JUN 9 2014

.SYNOPSIS...SOUTHWEST FLOW ALOFT WILL PREVAIL THROUGH MID TO LATE
WEEK...IN ADVANCE OF AN UPPER LEVEL TROUGH SLOWLY APPROACHING THE
REGION FROM THE WEST.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1045 PM MONDAY...

AN UPPER LEVEL DISTURBANCE (REMNANT VORTICITY MAXIMUM FROM SUNDAY'S
AFTERNOON ACROSS THE DEEP SOUTH) CURRENTLY CROSSING THE WESTERN
PIEDMONT OF NC. THIS FEATURE WORKING WITH AVAILABLE MOISTURE AND
SLIGHT TO MODERATE INSTABILITY TRIGGERED SCATTERED STRONG-SEVERE
CONVECTION EARLY THIS EVENING ACROSS THE WESTERN PIEDMONT WITH
NUMEROUS REPORTS OF TREES DOWN ACROSS SECTIONS OF RANDOLPH COUNTY.

A SURFACE TROUGH ELONGATED NORTH-SOUTH ACROSS THE COASTAL PLAIN MAY
SERVE AS A FOCUS FOR A FEW SHOWERS AND STORMS OVERNIGHT AS UPPER
LEVEL DISTURBANCE DRIFTS EAST. AS NEAR SFC ATMOSPHERE CONTINUES TO
STABILIZE...RISK OF SEVERE STORMS OVERNIGHT APPEARS WEAK/MINIMAL.

OUTFLOW FROM THIS EVENINGS STORMS WILL LIKELY SERVE AS A FOCUS FOR
ADDITIONAL CONVECTIVE ACTIVITY TUESDAY...ESPECIALLY ACROSS THE SOUTH
AND EAST SECTIONS OF THE FORECAST AREA. ANOTHER ROUND OF STORMS WAS
CROSSING THE DEEP SOUTH THIS EVENING. THE UPPER LEVEL SYSTEM
ASSOCIATED WITH THESE STORM EXPECTED TO DRIFT ACROSS CENTRAL NC LATE
TUESDAY MORNING. DEPENDING UPON HOW MUCH INSOLATION THE SURFACE
ATMOSPHERE RECEIVES IN THE MORNING WILL DETERMINE THE AMOUNT OF
INSTABILITY AVAILABLE TO FUEL THE STORMS. IF ITS MOSTLY-PARTLY SUNNY
IN THE MORNING...A MODERATELY UNSTABLE AIR MASS WILL LIKELY BE IN
PLACE BY MID DAY.  THIS COULD TRIGGER SCATTERED STRONG TO SEVERE
STORMS TUESDAY AFTERNOON ACROSS CENTRAL NC.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
AS OF 315 PM MONDAY...

OVERVIEW: SOUTHWEST FLOW ALOFT WILL STRENGTHEN OVER THE TN/OH VALLEY
TUE/TUE NIGHT AS AN UPPER LEVEL LOW (OVER THE CENTRAL PLAINS THIS
AFTERNOON) TRACKS EAST ACROSS THE CENTRAL MS RIVER VALLEY. SUBTLE
HEIGHT RISES AND SLIGHT AMPLIFICATION OF AN AN UPPER LEVEL RIDGE ARE
EXPECTED DOWNSTREAM ACROSS THE CAROLINAS /SOUTHEAST COAST/ AS THE
UPPER LEVEL PATTERN BECOMES INCREASINGLY AMPLIFIED ALONG THE MS
RIVER VALLEY.

CONVECTION: A MODIFIED ELEVATED MIXED LAYER WILL ADVECT EASTWARD
ALONG THE SOUTHERN PERIPHERY OF THE AFOREMENTIONED UPPER LEVEL
TROUGH OVER THE DEEP SOUTH GULF COAST AND THEN NORTHEASTWARD INTO
THE SOUTHEAST/CAROLINAS TUE AFTERNOON...WITH H7-H5 LAPSE RATES ON
THE ORDER OF 6.0-7.0 C/KM ACROSS CENTRAL NC. ASSUMING SEASONABLE
MOISTURE AND INSOLATION...MODERATE DIURNAL DESTABILIZATION (1000-
2000 J/KG MLCAPE) AND LITTLE OR NO CONVECTIVE INHIBITION WOULD BE
EXPECTED DURING THE AFT/EVE. HOWEVER...FORCING FOR ASCENT WILL ONCE
AGAIN BE CONFINED TO SHALLOW CONVERGENCE ALONG THE SEABREEZE AND/OR
A PIEDMONT TROUGH...PERHAPS DPVA ASSOC/W A SMALL AMPLITUDE
DISTURBANCE IN SW FLOW ALOFT OVER WESTERN PORTIONS OF THE STATE.
FURTHER COMPLICATING MATTERS...SUBSIDENCE MAY BE PRESENT TUE MORNING
THROUGH EARLY TUE AFTERNOON IN THE WAKE OF AN MCV EXPECTED TO TRACK
OFFSHORE THE NC COAST...ALONG WITH WEAK SYNOPTIC SUBSIDENCE UNDER
THE RIDGE AMPLIFYING OVER THE REGION. WITH THE ABOVE IN MIND...
CONSIDERABLE UNCERTAINTY IS PRESENT WITH REGARD TO CONVECTIVE
COVERAGE ON TUE...AND WILL INDICATE A 20-30% CHANCE OF SHOWERS AND
STORMS TUE AFT/EVE AND A SLIGHT CHANCE OF SHOWERS TUE NIGHT.

TEMPERATURES: AS LONG AS STRATUS DOES NOT DEVELOP AND PERSIST
THROUGH THE MORNING HOURS LIKE TODAY...STRONG INSOLATION AND RISING
HEIGHTS ALOFT WOULD SUGGEST HIGHS IN THE LOWER 90S. LOWS TUE NIGHT
IN THE UPPER 60S TO LOWER 70S.

SEVERE POTENTIAL: ALTHOUGH DEEP LAYER SHEAR IS PROGGED TO BE NO
HIGHER THAN ~20 KT OVER CENTRAL NC...RELATIVELY STEEP MID-LEVEL
LAPSE RATES...STRONG INSOLATION...SEASONABLE LOW-LEVEL MOISTURE...
AND MODERATE DCAPE (~1000 J/KG) ALL SUGGEST A CONDITIONAL POTENTIAL
FOR ISOLATED SEVERE STORMS CAPABLE OF PRODUCING DAMAGING WINDS AND
HAIL UP TO THE SIZE OF QUARTERS. -VINCENT

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
AS OF 145 PM MONDAY...

THROUGH WED NIGHT...FORECAST GUIDANCE SUGGESTS THE MID-UPPER LOW
OVER THE CENTRAL PLAINS WILL SPLIT...WITH THE PRIMARY LOW FORECAST
TO DRIFT INTO THE GREAT LAKES...AND ADDITIONAL VORTICITY AT THE BASE
OF THE TROUGH FORECAST TO DIG INTO THE SOUTHEAST STATES.
MEANWHILE...A MID LEVEL ANTI-CYCLONE WILL MIGRATE UP AND OFFSHORE
THE SOUTHEAST AND MIDDLE ATLANTIC COASTS. SO WHILE WEAK HEIGHT FALLS
ALOFT (ON THE ORDER OF 10-20 METERS/12 HR) WILL RESULT...LOW LEVEL
CONVERGENCE WILL REMAIN WEAK AND SHALLOW/CONFINED TO A PIEDMONT
TROUGH...WITH DEEPER AND MORE APPRECIABLE CONVERGENCE THROUGH THE
H85-925 LAYER - AND ASSOCIATED FOCUS/TRIGGER - EXPECTED TO HOLD OVER
THE EASTERN TN VALLEY AND SOUTHERN APPALACHIANS. AS SUCH...
THUNDERSTORM PROBABILITIES OVER CENTRAL NC WILL BE AT A RELATIVE
MINIMUM COMPARED TO SUBSEQUENT DAYS - IN THE LOW CHANCE RANGE. WHERE
STORMS DO OCCUR...HOWEVER...A HOT AND MODERATELY UNSTABLE AIR
MASS...ONE FUELED BY 7 C/KM MID LEVEL LAPSE RATES ATOP SFC
TEMPERATURES IN THE LOWER TO MIDDLE 90S...AND MID LEVEL FLOW OF
AROUND 25 KTS...WOULD SUPPORT PULSE/MULTI-CELL SEVERE WIND AND HAIL.
ANY STORMS THAT DO FORM SHOULD DIMINISH WITH NOCTURNAL
COOLING/INCREASING CINH...THROUGH THE EVENING. SOUPY...WITH AREAS OF
STRATUS AND FOG OVERNIGHT...AND LOWS IN THE UPPER 60S TO AROUND 70.

THU-FRI NIGHT: AN ELONGATED MID-UPPER LEVEL TROUGH AXIS BETWEEN THE
AFOREMENTIONED SPLITTING CENTRAL CONUS MID-UPPER LOW WILL THEN DRIFT
EAST INTO THE CAROLINAS THU-THU NIGHT...THEN BE REINFORCED BY A MORE
PROGRESSIVE/QUICKER NORTHERN SHORTWAVE TROUGH FORECAST TO TRACK
ALONG THE CENTRAL TO EASTERN CANADIAN/US BORDER FRI-FRI NIGHT. THE
LATTER FEATURE WILL PROPEL A COLD FRONT ACROSS THE CENTRAL
APPALACHIANS AND INTO CENTRAL NC LATE FRI-FRI NIGHT. DEEPER/
INCREASINGLY CONVERGENT LOW LEVEL FLOW WILL SUPPORT A HIGH CHANCE TO
LIKELY PROBABILITY OF SHOWERS AND STORMS MAINLY IN THE AFTERNOON
BOTH DAYS...BUT BOTH WEAKER MID LEVEL LAPSE RATES AND FLOW WILL
LIMIT ANY SEVERE THREAT....WITH SMALL STREAM AND URBAN FLOODING
PERHAPS A GREATER CONCERN. NOT AS HOT...BUT STILL HUMID...WITH HIGHS
IN THE MIDDLE 80S TO AROUND 90...AND LOWS AGAIN IN THE UPPER 60S TO
AROUND 70.

SAT-MON: THOUGH MEDIUM RANGE GUIDANCE SOLUTIONS DIVERGE WITH THE
LARGER SCALE FLOW ESPECIALLY ACROSS THE NORTHERN US DURING THIS
PERIOD...THEY REMAIN IN RELATIVELY GOOD AGREEMENT WITH THE FRONTAL
LOCATION/PROGRESSION INVOF THE CAROLINAS THROUGH THE WEEKEND. IT
APPEARS THE FRONT WILL BECOME INCREASINGLY W-E ORIENTED AND SETTLE
TOWARD THE SC BORDER BY LATE SAT OR SUN...THEN RETREAT NORTH/"WASH-
OUT" BY MON. AS SUCH...THUNDERSTORM PROBABILITIES WILL HOLD IN THE
CHANCE RANGE OVER THE SOUTHERN PIEDMONT AND SANDHILLS...TAPERING TO
20 PERCENT...OR LESS...OVER THE NORTHERN PIEDMONT...WITH
TEMPERATURES IN THE MID-UPPER 80S NORTH TO 90 DEGREES OR SO SOUTH.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 825 PM MONDAY...

24-HR TAF PERIOD: GENERALLY VFR CONDITIONS WILL PREVAIL... WITH THE
EXCEPTION OF ANY AREAS THAT SEE SHOWER OR THUNDERSTORM ACTIVITY.
KINT/KGSO ARE CURRENTLY BEING IMPACTED BY RAIN AND THUNDERSTORMS IN
THE AREA... AND THE ACTIVITY COULD POTENTIALLY IMPACT KRDU AND KFAY
OVER THE NEXT SEVERAL HORUS. WINDS WILL REMAIN GENERALLY SW...
EXCEPT WHERE AFFECTED BY THUNDERSTORM OUTFLOW.

LOOKING AHEAD: EXPECT AN ABOVE-NORMAL POTENTIAL FOR SHOWERS AND
THUNDERSTORMS THE REMAINDER OF THE WORK WEEK AS AN UPPER LEVEL
TROUGH SLOWLY APPROACHES THE REGION FROM THE WEST...WITH THE BEST
COVERAGE ON THU/FRI AS THE UPPER LEVEL WAVE SLOWLY CROSSES THE
CAROLINAS. -VINCENT

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

SYNOPSIS...VINCENT
NEAR TERM...WSS
SHORT TERM...VINCENT
LONG TERM...MWS
AVIATION...SEC/VINCENT

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